In conventional RF-receivers, analog filter circuitry is used to select the wanted intermediate frequency (IF) band prior to performing analog-to-digital conversion and demodulation. This analog filter circuitry is expensive and in many cases difficult to integrate with the digital circuitry, e.g. in VLSI (very-large-scale integration) CMOS (complementary metal-oxide-semiconductor) designs.
With the increasing availability of low-cost powerful digital signal processors and wideband analog-to-digital converters (ADCs) it has become feasible to omit the expensive and often complex analog filter circuitry and instead sample and process large parts of the reception bands at once. Apart from the cost reduction, new features, such as e.g. simultaneous reception of multiple broadcasts and background search algorithms for alternative radio stations, can be realized with this approach.
However, due to the wide passband of such a receiver, signal content outside a particular wanted frequency band may have a negative influence on the signal content within the wanted frequency band and thereby lead to difficult conditions at the final demodulation stage.
There may thus be a need for an improved wideband RF-receiver which is capable of dealing with the above problems.